A summary that just compresses a document — shorter version, same order, same emphasis — usually isn't useful, because it forces the reader to do the same work of finding what matters, just with less material to search through. A genuinely useful summary re-organises around what the reader needs to decide or do.
Lead with the decision or the conclusion
Weak: a summary that walks through the document section by section, ending with the recommendation on the last line. Strong: state the recommendation or conclusion first, then back it up. "Renew the contract at the current rate; the alternative supplier's discount doesn't offset the switching cost" tells a reader everything they need before they've invested any time.
Cut anything that doesn't change a decision
Long documents often include context, caveats, and methodology that matter to the original author but not to someone acting on the summary. Ask, for each sentence you're tempted to include: if I removed this, would the reader decide or act differently? If not, it belongs in the source document, not the summary.
Match length to the stakes, not the source
A forty-page report doesn't need a proportionally long summary just because that ratio feels tidy. It needs however many words it takes to convey the decision-relevant points clearly — sometimes three sentences, sometimes a page with a short list of risks. Let the content dictate the length, not a rule of thumb.
- State the bottom line first
- Support it with two or three concrete points, not everything from the source
- Name what changed or what's uncertain, if anything
If a reader has to read your summary and then still open the full document to find the actual point, the summary hasn't done its job, however accurately it captured the original.
